The following is opinion only.

You lose efficiency when redirecting your vision from the screen to the keyboard.

It's the same problem with touchscreens - mouse and keyboard operate on the same plane of motion. By touching the screen, you're breaking that plane. Additionally, you have to use cognitive resources to actually locate the button on the screen, rather than muscle memory, since there is no feedback of any sort from touching the screen.

The new Surface from MS actually does it right by re-orienting the work plane from vertical to horizontal, because the types of work you do in each orientation are different.

The keyboard in general, yes. But a strip at the very top of the keyboard, just below the monitor? It's nearly the same as redirecting your vision to the bottom of the screen. It's not the same as looking at the home row to find the H key or whatever.

Perhaps, but it still requires cognitive resources to locate the area you need to touch. With physical keys, you could rely on muscle memory and touch to delineate the proper key.

Now, it's just a smooth strip that you cannot discern one part of from another solely by touch.

I agree with that. Guiding your fingers by sight rather than by feel is not as good. I don't think it's because you're redirecting your vision, since it's not moving much, but the lack of tactile feedback is still problematic.